New types of cryptanalytic attacks using related keys
EUROCRYPT '93 Workshop on the theory and application of cryptographic techniques on Advances in cryptology
Related-key cryptanalysis of 3-WAY, Biham-DES, CAST, DES-X, NewDES, RC2, and TEA
ICICS '97 Proceedings of the First International Conference on Information and Communication Security
ICICS '02 Proceedings of the 4th International Conference on Information and Communications Security
Markov Truncated Differential Cryptanalysis of Skipjack
SAC '02 Revised Papers from the 9th Annual International Workshop on Selected Areas in Cryptography
Differential Cryptanalysis of DES-like Cryptosystems
CRYPTO '90 Proceedings of the 10th Annual International Cryptology Conference on Advances in Cryptology
Amplified Boomerang Attack against Reduced-Round SHACAL
ASIACRYPT '02 Proceedings of the 8th International Conference on the Theory and Application of Cryptology and Information Security: Advances in Cryptology
Flaws in Differential Cryptanalysis of Skipjack
FSE '01 Revised Papers from the 8th International Workshop on Fast Software Encryption
New Results on Boomerang and Rectangle Attacks
FSE '02 Revised Papers from the 9th International Workshop on Fast Software Encryption
Saturation Attacks on Reduced Round Skipjack
FSE '02 Revised Papers from the 9th International Workshop on Fast Software Encryption
Cryptanalysis of Skipjack Reduced to 31 Rounds Using Impossible Differentials
Journal of Cryptology
Improved Related-key Attacks on DESX and DESX+
Cryptologia
Security analysis of the full-round DDO-64 block cipher
Journal of Systems and Software
Related-key rectangle attack on 36 rounds of the XTEA block cipher
International Journal of Information Security
Weak-Key Classes of 7-Round MISTY 1 and 2 for Related-Key Amplified Boomerang Attacks
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Attacking 44 Rounds of the SHACAL-2 Block Cipher Using Related-Key Rectangle Cryptanalysis
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
EUROCRYPT'00 Proceedings of the 19th international conference on Theory and application of cryptographic techniques
Related-key rectangle attack on the full SHACAL-1
SAC'06 Proceedings of the 13th international conference on Selected areas in cryptography
Related-key rectangle attack on 43-round SHACAL-2
ISPEC'07 Proceedings of the 3rd international conference on Information security practice and experience
Related-key amplified boomerang attacks on the full-round eagle-64 and eagle-128
ACISP'07 Proceedings of the 12th Australasian conference on Information security and privacy
Attacking reduced-round versions of the SMS4 block cipher in the Chinese WAPI standard
ICICS'07 Proceedings of the 9th international conference on Information and communications security
Related-key rectangle attack on 42-round SHACAL-2
ISC'06 Proceedings of the 9th international conference on Information Security
Differential and rectangle attacks on reduced-round SHACAL-1
INDOCRYPT'06 Proceedings of the 7th international conference on Cryptology in India
A related-key rectangle attack on the full KASUMI
ASIACRYPT'05 Proceedings of the 11th international conference on Theory and Application of Cryptology and Information Security
Related-key rectangle attacks on reduced versions of SHACAL-1 and AES-192
FSE'05 Proceedings of the 12th international conference on Fast Software Encryption
Related-Key impossible differential attacks on 8-round AES-192
CT-RSA'06 Proceedings of the 2006 The Cryptographers' Track at the RSA conference on Topics in Cryptology
Related-Key boomerang and rectangle attacks
EUROCRYPT'05 Proceedings of the 24th annual international conference on Theory and Applications of Cryptographic Techniques
Related-key attacks on the full-round cobra-f64a and cobra-f64b
SCN'06 Proceedings of the 5th international conference on Security and Cryptography for Networks
Related-key rectangle attacks on reduced AES-192 and AES-256
FSE'07 Proceedings of the 14th international conference on Fast Software Encryption
A Cryptanalytic View of the NSA's Skipjack Block Cipher Design
ISA '09 Proceedings of the 3rd International Conference and Workshops on Advances in Information Security and Assurance
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Skipjack is a block cipher designed by the NSA for use in US government phones, and commercial mobile and wireless products by AT&T. Among its initial implementations in hardware were the Clipper chip and Fortezza PC cards, which have since influenced the private communications market to be compatible with this technology. For instance, the Fortezza card comes in PCMCIA interface and is a very easy plug-n-play device to add on to mobile and wireless systems to provide encryption for wireless transmissions. Initially classified when it was first proposed, Skipjack was declassified in 1998, and it sparked numerous security analyses from security researchers worldwide because it provides insight into the state-of-the-art security design techniques used by a highly secretive government intelligence agency such as the NSA. In this paper, commemorating a decade since Skipjack's public revelation, we revisit the security of Skipjack, in particular its resistance to advanced differential-style distinguishers. In contrast to previous work that considered conventional and impossible differential distinguishers, we concentrate our attention on the more recent advanced differential-style and related-key distinguishers that were most likely not considered in the original design objectives of the NSA. In particular, we construct first-known related-key impossible differential, rectangle and related-key rectangle distinguishers of Skipjack. Our related-key attacks (i.e., related-key miss-in-the-middle and related-key rectangle attacks) are better than all the previous related-key attacks on Skipjack. Finally, we characterize the strength of Skipjack against all these attacks and motivate reasons why, influenced by the Skipjack structure, some attacks fare better. What is intriguing about Skipjack is its simple key schedule and a structure that is a cross between conventional Feistel design principles and the unconventional use of different round types. This work complements past results on the security analysis of Skipjack and is hoped to provide further insight into the security of an NSA-designed block cipher; the only one publicly known to date.